孤岛状过渡金属磷化物表面修饰钙钛矿氧化物的原位构建及其双功能催化协同增效机制研究

Developing of highly efficient bifunctional catalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the most critical factor to improve the performance of lithium air batteries (LABs). Because of excellent catalytic activities, perovskite oxides have attracted much attention in LABs. But, there are big differences between their actual activities and intrinsic ones, which have important relationships with conductivity and surface/interface characterization of perovskite oxides. Based on reported publications and our preliminary works, transition metal phosphide (MxP) exhibits excellent ORR/OER catalytic activities, and high electron donating ability in composite materials. In this proposal, we develop a new strategy of in-situ surface modifying with island-liked MxP nanoparticles to generate heterogeneous structure and enhance actual ORR/OER catalytic activities of perovskite oxides. In this typical catalyst: firstly, both perovskite oxides and MxP have excellent ORR/OER catalytic activities, respectively; secondly, there is a synergistic enhancement effect between perovskite oxides and MxP; thirdly, confinement effect of island-liked MxP could effectively prevent the agglomeration of nanoparticles. Combined with in-situ characterizations, such as XRD、Raman, and electrochemical relaxed technology etc, the growth process and structure-function relationship of MxP/perovskite oxide heterogeneous structure will be studied, the catalytic mechanism and dynamic behavior for both the ORR and the OER will be investigated; Influences of MxP/perovskite oxide catalysts on the performance and cycle stability of LABs will be discussed by assembling 2032 coin cells. Theoretical and experimental results are compared and confirmed to get a proper theoretical model. The successful performing of this proposal will enrich the knowledge of controlling conductivity and surface/interface of perovskite oxides, and provide theoretical and technical supports for the developing of novel efficient bifunctional catalysts for LABs.

开发高效氧还原反应(ORR)和氧析出反应(OER)的双功能催化剂是提高锂空气电池性能的关键。钙钛矿氧化物以其高催化活性已在锂空气电池中备受关注。但实测催化性能远低于其本征催化活性，这与其电导率和表界面特性有关。文献报道和前期预研表明金属磷化物(MxP)具有ORR/OER催化活性，在与其它材料复合时有很强的给电子性。由此，项目提出在钙钛矿氧化物表面原位生长孤岛状MxP纳米颗粒，构建异质结构催化剂，在保持钙钛矿氧化物和MxP各自ORR/OER催化活性基础上实现二者之间的协同增强，并利用孤岛状MxP的限域效应，抑制纳米颗粒团聚。拟借助XRD、拉曼等原位表征方法和电化学驰豫技术研究异质结构催化剂的生长机理和构效关系，阐释催化增效机制和动力学；研究异质结构催化剂对锂空气电池性能和稳定性的影响规律；构建理论模型，拓展对钙钛矿氧化物电导率和表界面调控的认识，为开发新型高效双功能催化剂提供理论和技术指导。

受电导率和表界面特性等因素影响，钙钛矿氧化物的实际氧催化性能远低于其本征催化活性。针对这一问题，项目提出在钙钛矿氧化物表面原位生长孤岛状过渡金属磷化物(MxP)纳米颗粒，构建异质结构催化剂，在保持钙钛矿氧化物和MxP各自ORR/OER催化活性基础上实现二者之间的协同增强。项目执行细化为三个研究内容，并取得以下研究结果：1. 发展一种低温磷化制备过渡金属磷化物的合成路线，实现由过渡金属氧化物或金属/合金向MxP的直接转化，并在微观形貌上实现过渡金属磷化物由纳米片到孤岛状纳米颗粒再到量子点的精准控制。2. 发现钙钛矿氧化物原位脱溶现象，并藉此原位构建出系列CNTs@钙钛矿氧化物复合功能材料；实现对钙钛矿氧化物的非金属元素掺杂，提升催化性能。3. 成功实现孤岛状MxP@钙钛矿氧化物异质结的原位构建，讨论了钙钛矿氧化物结构（立方和层状）、金属磷化物种类（一元和合金）等因素对异质结构催化性能的影响，并通过理论计算，从电子结构、氧吸脱附等角度厘清异质结构催化剂的氧催化性能协同增效机制。项目拓展了对钙钛矿氧化物电导率和表界面调控的认识，可为开发新型异质结构高效氧催化剂提供理论和技术指导。